The present invention relates to method and apparatus for monitoring and evaluating the operation of rotary element cleaning devices from the exterior of a vessel based upon sound analysis.
There are many machines that include a vessel having cleaning elements (e.g., rotary, reciprocating, stationary, etc.) contained within them for the purpose of cleaning items within the vessel, or even the vessel itself. Consider, for example, the common dishwasher. A dishwasher typically comprises a closed vessel with a rotating cleaning device located at the bottom of the vessel. When the dishwasher is operating, there is no way of seeing inside to determine if the cleaning elements are operating properly. Frequently, a fork or knife may fall through the dish rack and block the rotation of the rotating spray arm, which is part of the rotary cleaning element. The result of the blockage is a poor cleaning cycle which in turn results in unclean dishes. However, the first indication of this problem is at the end of the cleaning cycle when the dishwasher is opened to empty the contents, and at this point it is too late, as the time and resources associated with operation of the dishwasher have already been consumed.
Current industry solutions for this problem include installation of a window in the vessel, which gives a visual accounting of the cleaning activity, or the use of an electronic pressure switch inside the vessel that senses the impact of the spray coming from the spray arm. Both have significant shortcomings.
Most vessels do not have windows since they are very expensive to install and labor intensive to monitor. To install a window an opening must be cut through the vessel wall. The interior of the enclosure must then be illuminated so the observer may see through the window into the vessel. Even with the illumination, the observer may not be able to view the operation of the cleaning elements through the window due to cleaning solution collecting on the inner surface of the window. In the case of a rotary cleaning element, all the observer can tell is that the rotary element is (or is not) rotating and/or spraying liquid; it is very difficult, if not impossible, to make significant qualitative assessment of the operation of the rotary element. The problem is further complicated if two or more cleaning devices are operated simultaneously within the vessel. One may stop while the other(s) continues to operate. The observer may see the spray from the properly-operating device striking the window and be given the false impression that all of the devices are operating properly. Mistakenly the observer may believe that all is well.
Installation of a pressure switch that generates a signal when impacted by the spray from the cleaning devices is a more reliable solution than the above-described window solution. The primary downfall to pressure switches involves environmental considerations which may degrade the switch and/or its performance, such as high temperatures, pressurization and caustic cleaning solutions. As in the case of the window, installing the pressure switch also requires a penetration through the vessel wall. The positioning of the switch is critical since to be reliable it must receive xe2x80x9chitsxe2x80x9d from the cleaning spray on a regular basis. The only location meeting this requirement may be a very small area relative to the spray device. A poorly placed sensor will likely yield unreliable indications.
As noted above, both the window and the pressure switch solutions require penetrations to be made through the vessel wall. In addition to being expensive, in a great many instances it is not possible due to the intended usage, construction, or placement of the vessel within a facility.
It is common in the food, beverage and drug industries to utilize large vessels for processing, storing and/or transporting product. For example, tanks are used in the production, storage and transporting of whisky, beer and wine. These tanks range in size from several hundred gallons to tens of thousands of gallons. In order to produce an acceptable product for sale and/or to satisfy FDA regulations, these tanks must be hygienically cleaned between usages. Specialized cleaning equipment has been developed that can be inserted or in many cases sealed into the tanks to perform the cleaning process.
There are many examples of such cleaning systems. For example, Toftejom, Inc. of Pasadena, Tex.; Sellers Cleaning Systems of Piqua, Ohio; and Gamma Jet Cleaning Systems, Inc. of DeVault, Pa., all manufacture and sell such devices. These devices typically have one or more spray heads that have both horizontal and vertical rotational patterns. Examples of such cleaning devices can be found in U.S. Pat. No. 6,123,271 and U.S. Pat. No. 5,954,271.
FIGS. 1A-1C and 2 illustrate, respectively, a typical prior art spray head and a typical tank environment in which this prior art spray head is used. Referring to FIGS. 1A-1C, an inlet pipe 100 has a rotational sleeve 102 on which a spray head 104 is attached. Spray head 104 has situated around its perimeter a plurality of discharge nozzles 106 (three are shown in FIGS. 1A-1C). Spray head 104 rotates along axis A2 around the inlet pipe 100, and also rotates along axis A1, thereby resulting in a xe2x80x9cthree-dimensionalxe2x80x9d spray pattern.
Referring now to FIG. 2, a tank 210 has an inlet pipe 200 inserted therein, with the inlet pipe 200 having, in this example, two spray heads 204A and 204B, each of which correspond to the spray head detailed in FIGS. 1A-1C. In operation, the entire assembly (the inlet pipe 200 and the rotational spray heads 204A and 204B) is inserted into the tank 210 to be cleaned, and pressurized water is introduced into the inlet pipe 210. In a well known manner (see, e.g., the above-referenced U.S. Pat. Nos. 6,123,271 and 5,954,271), the introduction of the pressurized water into inlet pipe 200 causes the rotational movement of the spray heads 204A and 204B along both axes A1 and A2 of FIGS. 1A-1C, generating a spray pattern as illustrated generally by the solid arrows and dotted line arrows of FIG. 2. It is understood, of course, that the spray pattern illustrated in FIG. 2 is shown merely to illustrate the general idea of this prior art system and is not intended to shown the precise spray pattern of the spray heads.
Cleaning devices of the type described above operate quite well and are used throughout industry for cleaning purposes. However, it is often difficult to determine if the cleaning heads are functioning properly since, like the dishwasher described above, the operation of the device occurs inside the sealed vessel and out of the view of the operator. To ensure that the products contained in the vessels are not contaminated due to a poor cleaning cycle caused by a cleaning device malfunction, the operation of the cleaning devices should be monitored on a regular basis. Since this is difficult to accomplish, the common practice is to (1) periodically test the cleaning equipment outside of the vessel and/or (2) test the final product for contaminants after the fact. Periodically testing the cleaning equipment outside of the vessel, of course, only assures that the device is working when it is being tested, and not during operation. Testing the final product for contaminants after the fact, on the other hand, runs the risk of producing a bad batch of product and that must therefore be disposed of. In many instances the contaminated product is considered hazardous waste and must be disposed of at great cost and/or difficulty. Accordingly, it would be desirable to have a cleaning head monitoring system that can, on a real time basis, and from the exterior of the vessel, accurately monitor the operation of the cleaning head during the cleaning operation.
The present invention utilizes sound detection techniques and sound discrimination techniques to analyze the real time ongoing operational sounds generated during the operation of cleaning heads operating within a vessel to determine if the cleaning heads are operating properly. The term xe2x80x9csound,xe2x80x9d as used herein, includes mechanical vibrations both within and outside the perception of human hearing.
During a typical cleaning operation pressurized cleaning solution is dispensed through a nozzle assembly inside the vessel. In the case of a rotating spray head, as the nozzles rotate the spray moves about the interior of the vessel creating a unique sound pattern. By placing one or more pickups on the exterior of the vessel the sound is captured and fed to an analyzing device for analysis. Key properties such as, but not limited to, sound pressure levels, amplitude variations, spectral content, and rotational information are extracted and analyzed against the reference parameters.
In a preferred embodiment, xe2x80x9creference parametersxe2x80x9d (also referred to as xe2x80x9csound signatures,xe2x80x9d xe2x80x9creference sound values,xe2x80x9d xe2x80x9creference frequency patternsxe2x80x9d) derived from a properly functioning cleaning cycle are compared with equivalent parameters derived on an ongoing basis during subsequent cleaning cycles (referred to herein as xe2x80x9congoing operational sound values,xe2x80x9d xe2x80x9ccaptured sound values,xe2x80x9d xe2x80x9cmeasured frequency patternsxe2x80x9d). Based upon the comparison, it is determined whether or not the cleaning heads are functioning properly. In a preferred embodiment, filtering techniques are used to increase the accuracy of the comparison.